This invention relates generally to the advances in medical systems and procedures for prolonging or improving human life. More particularly, this invention relates to an improved method and system for destroying cancerous bone metastatic tumors and relieving pain symptoms caused by such tumors or metastatic disease.
A very large percentage of all cancerous disease which spreads, or metastasizes, results in growth of metastatic tumors, called meta stases, in the bony structures of the patient""s body. In advanced metasta tic bone disease, the patient experiences excruciating pain due to pressure of the tumor on surrounding nerves, tissue, and the innervation of the bone and endosteum or periosteum itself. The quality of the patient""s life at this point can deteriorate quickly, and the levels of pain become intolerable.
The common methods of treating metasta tic cancerous tumors include radiation therapy. Application of X-ray radiation therapy can slow the progression of bone metasta tic cancer growth but usually cannot halt it. Moreover, some bone metastases are relatively unresponsive to radiation therapy. Another problem with radiation therapy is that it causes death of the bone marrow which produces the red blood cells that are vital to life. Therefore, only a limited amount of X-ray dosage can be given before critical destruction of bone marrow takes place. Another limitation of radiation therapy is that once it has been administered up to a certain dose level, further application of the radiation therapy typically is prohibited. This is to prevent overdosing of the surrounding normal tissue and organs in the patient. In sum, radiation therapy has a limited repeatability.
Radiation therapy also is a relatively complex and expensive procedure. Localization of the cancerous tumor with respect to the therapeutic X-ray beam may be difficult as a result of inaccurate patient positioning on an X-ray delivery device such as a linear accelerator (LINAC). To be effective, fractionated or repeated doses of radiation have to be given over a period of weeks or months. This is expensive in terms of equipment time and personnel costs, and can be inconvenient for a patient who is ill.
Localization of the metastatic tumor volume in the X-ray beam is a difficult technical problem which remains a challenge for radiation therapy. As a consequence of the indefiniteness of the tumor localization in the X-ray beam, larger margins of dosimetry must be given. This further puts at risk sensitive, normal tissue or organs that are nearby the bone and the bone tumor. Excess delivery of radiation to normal tissue can be very harmful with severe side effects and deterioration of the patient""s condition and quality of life.
Chemotherapy is another method of treating bone metastases. This is a systemic treatment that can cause severe sickness in and inconvenience to the patient. Because of the toxicity of chemotherapy, the rest of the body""s systems are put at risk. Moreover, the effectiveness of chemotherapy in targeting the bone tumor itself is limited.
The treatment of a primary benign bone tumor using a percutaneously placed radiofrequency electrode has been reported by Rosenthal, et al. in their paper entitled xe2x80x9cPercutaneous Radiofrequency Treatment of Osteoid Osteomas,xe2x80x9d Seminars in Masculoskeletal Radiology, Volume 1, Nov. 2, 1997. A radiofrequency electrode was inserted into the small primary bone tumor and connected to a radiofrequency power source to heat the bone tumor so as to destroy it. A bone tumor which they destroyed was of a type called xe2x80x9costeo-osteoma,xe2x80x9d which is a relatively rare disease. They were successful in heating the osteo-osteoma tumor and destroying it completely in some cases. Osteo-osteomas are typically small tumors with a diameter of 1 to 2 centimeters. Rosenthal did not contemplate treating larger bone cancer or the painful condition they create.
It should be recognized that the theory behind and practice of radiofrequency (RF) heat lesioning has been known for decades, and a wide range of RF generators and electrodes for accomplishing such practice exist. For example, equipment for performing heat lesions is available from Radionics, Inc., located in Burlington, Massachusetts. Radiofrequency (RF) ablation is well known and is described in medical and clinical literature. To that end, a research paper by E. R. Cosman, et al., entitled xe2x80x9cTheoretical Aspects of Radiofrequency Lesions in the Dorsal Root Entry Zone,xe2x80x9d Neurosurgery, Vol. 15; No. 6, pp. 945-950 (1984), describing various techniques associated with radiofrequency lesions, is incorporated herein by reference. Also, by reference, a research paper by S. N. Goldberg, et al., entitled xe2x80x9cTissue Ablation with Radiofrequency: Effective Probe Size, Gauge, Duration, and Temperature on Lesion Volume,xe2x80x9d Acad. Radiol., Vol. 2; pp. 399-404 (1995), describes techniques and considerations relating to tissue ablation with radiofrequency energy.
In addition, a paper by S. N. Goldberg, et al., entitled xe2x80x9cHepatic Metastases: Percutaneous Radiofrequency Ablation with Cool-Tip Electrodes,xe2x80x9d Radiology, Vol. 205, No. 2, pp. 367-373 (1997), describes various techniques and considerations relating to tissue ablation with radiofrequency electrodes having cooled electrode tips. Cooling of the electrode can result in larger volume of RF heating due to the extension of the heating volume to greater radii away from the electrode. Cooled ablation electrodes may maintain tissue near the electrode at temperatures that are below tissue ablation temperatures.
A technique which is minimally invasive, safe, and effective for ablating large metastatic bone tumors for the purpose of destroying the tumor and for the purpose of relieving pain associated with such metastases is desirable. Accordingly, an effective technique for performing RF electrode ablation of metastatic tumors is desirable for the purpose of reducing the volume of the metastatic tumor, for killing the entire tumor volume, or at least a portion of the tumor volume, and for the alleviation of pain for the patient.
The present invention is directed towards a system and procedure for heat ablation of bone metastases through use of a probe which is advanced either percutaneously or under direct surgical approach into the bone metastasis or into peri-osseous tissue (tissue on, near, surrounding, or in the bone). The guidance of the probe into the bone metastasis can be assisted by various imaging methods such as ultrasound, CT, MRI, stereotactic, or other imaging or image-guided system methodologies. The advantages of the present system and method reside in their combined simplicity, economy, control, consistency, enablement of good ablation position and shape, total destruction of metastatic tumor and clinical effectiveness to reduce the tumor volume. Another advantage of the present system and method is that in some cases it can provide instant pain relief for the patient who suffers from the advancement of metastatic bone tumors.
In one embodiment, the technique of the present invention involves inserting a rigid, tissue-piercing radiofrequency (RF) electrode through the patient""s skin into the region of the tumor, as visualized under a CT tomographic scan. The RF electrode can be of a cooled type, as described by Goldberg, et al. in the reference above. Application of sufficient power from an RF generator connected to the electrode will deliver heat to the metastatic tumor, thereby destroying part or all of the tumor volume by reducing the tumor to a necrotic fluid mass which may be absorbed by the patient""s body. The use of multiple and/or curved electrodes placed into the tumor volume can supplement the shaping of the RF ablation heat region. This application of an RF heating electrode or other type of thermal probe or pulsed RF element into the tumor, surrounding bone, or peri-osseous tissue can also relieve pain in accordance with the present invention.
In contrast to radiation therapy and chemotherapy, the RF electrode ablation technique is minimally invasive, simple, and well tolerated by the patient. For example, this technique may be performed when the patient is lightly sedated. The procedure can take less than an hour and is minimally invasive thereby reducing the risk of bleeding, infection, surgical complications, radiation risks, and morbidity and mortality in comparison to radiation and chemotherapy methods.
The present system and method has the further advantage in many cases of relieving the excruciating pain associated with the presence of the metastatic tumor. This pain relief can, in some cases, occur almost instantaneously with the application of the radiofrequency ablation heat. The adjunct of pain relief can instantly and dramatically improve the quality of life of the patient suffering from the metastatic bone cancer.
A further advantage of the present technique is that by use of a cooled tissue-piercing electrode, very large ablation volumes can be achieved to treat the very large volumes that are common for metastatic tumors in the bone. It should be noted that Rosenthal, et al. in the article referred to in the Background section did not contemplate the use of cooled electrodes for achieving very large ablation volumes, nor did they contemplate using thermal ablation systems and methods for the treatment of metastatic bone disease and associated pain, which is a common, invasive, and aggressive problem for patients with terminal malignant cancer.
Also, the present technique may avoid injury to surrounding tissue, in contrast to such risk of injury posed by radiation therapy. Radiofrequency ablation does not destroy red bone marrow in surrounding bones that are outside the target area (the ablation heat volume). In contrast, this is a significant problem in poorly directed X-ray radiation dosimetry. The RF ablation method enables a total kill of all or part of the tumor within the ablation volume. This volume can be graded by the surgeon by the degree of power applied and the temperature in the ablation volume.
A further advantage of the RF ablation technique is that it is repeatable. For example, in a second session, further ablation of bone tumors can be performed with relatively minimal risk to the patient.
A significant advantage of the RF ablation method for bone metastases is that it is clinically effective and economical. The procedure is relatively simple in contrast to regimes of chemotherapy and radiation therapy. It has been found to be very clinically effective at reducing metastatic tumor volumes and providing dramatic pain relief for patients suffering from this disease. The radiofrequency electrodes may be simple structures that can be manufactured and sold at economical levels, as compared to structures used with chemotherapy and radiation therapy. Further, all or part of the metastatic bone tumors may be uniformly killed by radiofrequency heating. This is not the case for radiation therapy where some tumors are not sensitive to X-rays and where dose limitations (e.g., due to the critical location of the tumor) prevent escalation of X-ray dose.
Moreover, radiofrequency ablation can be performed during the same intervention as a biopsy of a metastatic tumor, thus making the procedure even simpler because it can be performed in a single session. This has the advantage of great convenience for the patient, surgeon, and hospital, and reduces substantial management costs, operating theatre expenses, and logistics as would occur for radiotherapy and chemotherapy. The patient can undergo the radiofrequency ablation in one simple session lasting typically one hour. This is an advantage in time effectiveness compared to radiation therapy or chemotherapy, which require weeks and sometimes months of a complex regimen of applications which are expensive and inconvenient for a patient who may have to travel a significant distance to the hospital center.
Another advantage of the present invention is that it is minimally invasive and easily tolerated by the patient. Often patients with advanced cancer and bone metastases are in frail health and cannot tolerate surgery or protracted therapies. Heat ablations offer them a convenient, simple, and minimally intrusive way to handle a disease state for which there are few or no other clinical options left. The present invention can reduce the dependency of the patient on chemotherapy or pain relieving drug therapies, either of which can severely reduce the patient""s quality of life.
In one embodiment of the invention, image-guided data such as CT, MR, or X-ray information is used to plan the placement of RF electrodes. This data can be used in a computer with a graphic display to visualize and plan the placement of electrodes in the bone, bone tumor or peri-osteum for proper ablation coverage of heat distribution. Image guidance during the electrode placement and use of a stereotactic-guided, electrode support, and/or digitizer/image-guided navigator helps in placement and control of the electrodes into or near the tumor.